I would have cropped out the building on the left and moved into the flower a lot closer. In that way you would have been able to get more color into your image and enhance the flower a lot more. The shallow DOF is good as you have it directing the main focus onto the flower.
I like the colors in this photo but I think it could be improved quite a bit overall. The focus seems off to me but I do like the way the trees in the background are out of focus. It might be more pronounced if you could open up the lens more (use the largest aperture available). The problem with doing this is that the focus on the subject becomes very critical. I would try to take this picture from a slightly different angle to exclude the roof of the building. Another suggestion would be to use the maximum resolution allowable for your challenge submissions. I gave this one a 3 but I think with some work it could do much better.
Would have liked to see this as more of a macro and you unfortunately cut off the top of the bloom. Background is somewhat busy for me taking away from the subject.